Method of prevention of nozzle fouling



Oct. 12, 1965 M. BRENNER 3,211,377

METHOD OF PREVENTION OF NOZZLE FOULING Filed June 28, 1963 United StatesPatent 3,211,377 METHOD OF PREVENTION OF NOZZLE FOULING Mannie Brenner,Cambridge, Mass., assignor to W. R. Grace & (30., Cambridge, Mass, acorporation of Connecticut Filed June 28, 1963, Ser. No. 291,417 4Claims. (Cl. 2391) This invention relates to the application ofcontainer sealing compositions to closures, and more particularly to amethod and means of preventing the build-up of compositions on anapplicator nozzle.

The gasket which forms the hermetic seal between the body and the end ofa can is applied to the end in liquid form. The sealing composition isejected through a small nozzle which is placed directly above thesealing periphery of the can end. At the moment of lining as theoperation is known in the container sealing industry, the end, supportedon a continuously rotating chuck, turns beneath the nozzle. As a result,a peripheral strip of composition is placed on the sealing area.

Nozzle build-up is a difficulty which most usually occurs in the liningof can ends with sealing compositions which contain a solvated orpartially solvated elastomer. It is particularly severe when ends arelined on the shoulder, i.e., the inner wall of the channel, rather thanon the floor of the channel or against the cur i.e., the incurvedmargin. This is a placement which is preferred by certain canmanufacturers and is often used for cans which must withstand internalpressure such as beer and soft drink cans. Since the can end at themoment it receives the lining is spinning at 2000 to 2500 rpm. thesealing composition would be thrown oh the shoulder and packed under thecurl were it not a sticky and comparatively stiff plastic mass. Thissticky adhesiveness, necessary to prevent displacement, is a main causeof build-up, for the composition sticks to the nozzle as well as to theend.

In contrast to many compositions which may be run for hours withoutfouling the machine, these compositions require frequent shut-down forclean-up. On one type of lining machine where a turret of nozzles fixedon radial spokes as well as the can ends beneath the nozzles travel in acircular path, the trouble is compounded. The large centrifugal forceand turbulent air patterns set up by a large revolving assembly causesso much build-up that down time is excessive and approaches runningtime.

Since most solvent-based sealing compositions contain elastomeric highpolymers which in the liquid sealing composition are solvated to somedegree, none are Newtonian fluids. A few where solvation is negligiblecan be Elassed as Bingham Plastics. Others exhibit much more complexflow characterstics.

The most troublesome class of compounds may, for the descriptive purposeof setting forth their troublesome behavior, be called elastic. As theflow from the nozzle to the can end ceases, one end of the stream ofcomposition is anchored on the revolving can end, the other extends tothe nozzle. As the radial distance increases, the strand stretches, thenbreaks. The ends of the strand fly back violently as if one had snippeda stretched rubber band. The strand attached to the can end usuallysnaps back into the can end channel and does no harm, but the strandattached to the nozzle snaps back and sticks to it.

3,211,377 Patented Oct. 12, 1965 Shortly, so big a deposit builds up onthe nozzle that shut-down of the machine is imperative. The nozzle mustbe cleaned.

I have discovered that if the exterior surface of the tip iscontinuously covered with some fluid which wets the metal surface, thehead of fluid which otherwise would collect at the tip will be draggedfrom it by the emerging jet of sealing compound. Presumably it isdragged away as a sheath of fluid on the surface of the emerging stream,for the performance of the strand which forms after the nozzle shuts offis greatly modified. The strand will drop away from the tip rather thanfly back on to it. In consequence, much longer periods of noninterruptedmachine production result.

It is the purpose of this invention to reduce to a material degree theamount of build-up of such compositions on the nozzles of the liningmachinery and by reducing the amount of build-up to permit the machinesto run for much longer times without the necessity of shut-down andclean-up.

The fluid may be led on to the tip directly through a capillary tubemaintained in contact with the tip surface, or preferably the tube maybe led into a small bore in the tip-holding nut. In this instance,either the thread space or a channel especially cut at the root of thethread forms a header from which the liquid may flow down the exteriorsurface of the tip.

The nature of the liquid is primarily governed by the nature of thesealing composition, and consequently will vary widely. The compounder,having this disclosure in hand, can readily select fluids which will wetthe nozzle tip yet which are compatible with his composition. His choicemay run from petroleum solvents such as hexane, oils such as palm,cyclic hydrocarbons such and toluol and xylol, glycols such as ethyleneand propylene glycols, aliphatic esters such as ethyl acetate, ketones,e.g., methyl ethyl ketone, alcohols, e.g., octyl alcohol, and,particularly when the sealing composition is a water base dispersion,water in which a wetting agent is dissolved.

As a general statement, the liquid which is the base of the sealingcomposition will be suitable as the fluid for the sheath, e.g., if thepolymeric constituent of the sealing composition is a solvatedsuspension in hexane, hexane will be found a suitable fluid and willreduce build-up if it is fed through the capillary.

The nozzles used on container closure lining machinery usually comprisea nozzle tip made of some abrasion resistant alloy. The tips areprovided with axial bores through which the compound which is underconsiderable pressure is ejected, and near the lower end of the bore aconical valve seat is formed which is closed by a needle which is raisedand lowered by an actuator mounted directly above and in line with thetip. A number of bore diameters are required to adapt the tip to thelining requirements of the particular closure. Hence, the tips areinterchangeable and are held to the nozzle body by a shouldered nutwhich engages a base flange formed on the tip.

In the drawings,

FIG. 1 is an elevation of one form of nozzle equipped with the liquidfeed device.

FIG. 2 shows a tip and a conical wind shield.

FIG. 3 shows a tip modified with an external liquidconducting grooveleading toward the orifice.

FIG. 4 shows a modified tip having a. radial, flat external face.

FIG. 5 shows a tip assembly in which liquid is fed to a header space,and

FIGS. 6 and 7 show vertical sections of tips which sometimes will befound to improve the effectiveness of this invention either on machinesof varying type or with compounds having differing flow characteristics.

Referring to FIG. 1, the nozzle 10 is one of several types of nozzlesused. All, however, bear a general similarity. The mechanism whichraises and lowers the needle, whether mechanical or electro-pneumatic,is housed in the casing 11. Sealing composition enters the chest section12 of the nozzle through a conduit, not shown. The valve seat is alwaysformed in the interchangeable tip 13 (the bore size and often itsparticular shape must meet the demands of various closures). Tip 13 isheld in place by the engagement of its base flange 20 with theshouldered nut 15 screwed on to the threaded extension 14 which isformed on chest 12.

The fluid is supplied to the external surface of the tip 13 by thecapillary tube 16 which fits through a small hole 17 bored in nut 15.The end of capillary 16 lies directly against the surface of the tip 13.

Fluid is contained in the reservoir 18 here shown in section. Instead ofsmall individual reservoirs, the fluid may be conducted through tubingand several nozzles may be fed from one source. Reservoirs such as 18should, however, extend horizontally rather than vertically to minimizethe variation in head. Reservoir 18 is supported on the nozzle by thebracket 19.

Should the machine be of the revolving turret rather than the linearfeed type, the liquid will travel around the tip rather than flow downits surface. Much will be thrown off before it reaches the margin of theorifice. To prevent this, a groove, 21, may be cut in the conical faceof the tip 130: as shown in FIG. 3, or a flat, radiused face 22 may beformed on the modified tip 13b (FIG. 4). However, when the nozzlesthemselves move in a rotary path, if fluid is to be prevented fromrunning around the tip, the channel 21 or flat face 22 must face thecenter of the rotation, but the line of flow on the surface of the tipmust be directed outwardly towards the periphery. If the nozzle istilted or so shaped as to point the line of flow of fluid on the tipsurface towards the center of rotation, fluid will move around the tiprather than flow towards the orifice.

Small grooves or nick-s as shown at 23, FIGS. 4 and 5, may also beground in the flange portion of the tips. One or a multiple of nicks 23will then lead fluid from the header space 24 (FIG. 5) to the exposedtip surface. In this case, the nut 15 has the lead hole bore 17 in aposition where the capillary 16 is led directly into header 24 (thespace between the base flange and the nut 15).

In the rotary turret type of machine windage may be a problem. Ifturbulent air flow upsets the surface flow of liquid, it may be shieldedby the tip shield 25. This is a thin metal spinning slightly larger thanthe tip 13 and is held in spaced relation to the tip 13 by the nut 15.Capillary 16 enters the shielded space 26 through a small hole in theshield.

Modification of the usual tip improves performance. Considering the tipas a cone, the best results are achieved when the orifice occupiesalmost the entire area of its upper base. In other words, the tip shouldbe ground so as to make the margin surrounding the orifice sharp andnarrow (see FIGS. 6 and 7). Thus, the external dimensions of the tip arerelated to the diameter of its bore to provide a sufficiently smallsurface area to permit fluid on the extremity of the tip to come intodirect contact with each emerging jet of sealing composition.

FIGS. 6 and 7 illustrate two of the orifice configurations which may beused. Bore size (which determines the width of the lining) and flowcharacteristics of the composition dictate the choice. FIG. 7 shows anangle delivery tip. It is useful in shoulder lining.

4 Example I Tests using five different tips with five different sealingcompositions were run on one machine under conditions tabulated below:

Tip Type 1 2 3 4 5 Composition A B C D E Percent total solids incomposition 47. 5 44. 5 43. 5 54. 0 39. 0 Viscosity, centipoises(Brookfield Viscosimetcr) 6, 2,050 2, 600 9, 000 1, 750 Production speed(ends per min.) 350 210 150 350 300 Chuck Speed (r.p.m.) 2, 200 1, G591, 710 2, 212 1, 900 Flow through capillary (seconds per drop) 7. 5 7. 57. 5 7. 5 Varied Diameter of orifice (inches) .028 .028 .028 O28 028 Canend size 307 401 307 307 211 Dry weight of lining (mg 77 99 80 84 75Specific gravity (dry film) 1. 38 1. 33 1.38 1. 25 1. 23

RESULTS No. of Amount of Temp. 0! Ends Build-up Composition,

A 100 B 106 C 115 115 D-. 115

E 115 Skelly 100 drop/5 sec.

1 Several thousand.

The amount of fluid supplied to the nozzle was determined by stoppingthe machine following flow adjustments which had been found to givesatisfactory lining performance, and then measuring the volume of liquidwhich dropped from the nozzle. The flow rate was found to lie betweenone drop every 4 to one drop every 10 seconds-the most effective ratebeing one drop every 7% seconds. Assuming 10 mg. of hexane to be theweight of one drop, 60150 mgs. of hexane per minute is an effective flowfrom the nozzle tip. At such rates, can end sizes varying from 211-401may be lined at from -350 ends per minute. Other fluids may be found torequire different drop rates to achieve maximum effectiveness.

I claim:

1. The method of reducing build-up of container sealing compositions onthe tips of lining machine nozzles which tips are of generally conicalconfiguration and possess a lower and upper base which includes Wettingthe surface of the emerging jet of container sealing composition with acompatible liquid, application of the liquid to the jet being made byconducting the liquid to the exterior surface of the tip through acapillary passage, and relating the external dimensions of the tip tothe diameter of its bore by reducing the surface area of the upper basesuificiently to permit fluid on the extremity of said tip to come intodirect contact with each emerging jet of the sealing composition.

2. The process of claim 1 wherein the liquid in its descent to theextremity of the tip is shielded from air currents by a surroundingshield maintained in spaced relation to the exterior surface of the tip.

3. The process of claim 1 wherein liquid is conducted to the extremityof a nozzle tip despite the centrifugal force of a revolving nozzleassembly by forming a notch 0n the exterior surface of the nozzle tipleading from the base to the margin at the tip orifice and positioningthe notch in the plane of a radius of the nozzle rotation in the liningmachine, facing the center of rotation.

4. The process of claim 1 wherein liquid is conducted to the extremityof a nozzle tip despite the centrifugal force of a revolving nozzleassembly by forming a flat radial face on the tip and directing saidface towards the center of rotation of the nozzles and in a plane normalto a rotational radius of the machine, and said radial face beingpositioned vertically so as to direct the flow of fluid outwardly fromthe center of rotation of the nozzles and simultaneously downwardlytoward the tip of the nozzle.

References Cited by the Examiner UNITED STATES PATENTS 4/ 16 Englemann2393 14 1/34 Weiss 239--1 9/ 34 Collasure 239-434 1/ 46 Radonich 239-l7/61 Hjulian 239-424 3/62 Gascoigne et al 239424 FOREIGN PATENTS 3/58Australia.

5/57 Germany.

1/ 62 Great Britain.

2./ 34 Switzerland.

EVERETT W. KIRBY, Primary Examiner.

1. THE METHOD OF REDUCING BUILD-UP OF CONTAINER SEALING COMPOSITIONS ONTHE TIPS OF LININ MACHINE NOZZLE WHICH TIS ARE OF GENERALLY CONICALCONFIGURATION AND POSESS A LOWER AND UPPER BASE WHICH INCLUDES WETTINGTHE SURFACE OF THE EMERGING JET OF CONTAINER SEALING COMPOSITION WITH ACOMPATIBLE LIQUID, APPLICATION OF THE LIQUID TO THE JET BEING MADE BYCONDUCTING THE LIQUID TO THE EXTERIOR SURFACE OF THE TIP THROUGH ACAPILLARY PASSAGE, AND RELATING THE EXTERNAL DIMENSIONS OF THE TIP TOTHE DIAMETER OF ITS BORFE BY REDUCING THE SURFACE AREA OF THE UPPER BASESUFFICIENTLY TO PERMIT FLUID ON THE EXTREMITY OF SAID TIP TO COME INTODIRECT CONTACT WITH EACH EMERGING JET OF THE SEALING COMPOSITION.